Localized illumination device

ABSTRACT

Illumination apparatus for use in localized illumination applications, such as an automobile dashboard. The apparatus includes a light emitting diode mounted on a metallized circuit board; a TIR lens mounted over the light emitting diode to collect light emitted from the light emitting diode and to direct the light in a single direction; and a light pipe disposed over the light emitting diode and the TIR lens. The light pipe has walls extending from the circuit board to a plane above the circuit board such that directed light from the TIR lens is channeled through the light pipe to the plane. The apparatus can also include a cover disposed in the plane over the light pipe. The cover may be integrally molded to the light pipe and have an icon configured therein, such that the icon is illuminated by the light from the light emitting diode. A lens may also be placed over the cover of the light pipe to create a focused image of the icon, thereby maximizing the light emitted by the light emitting diode at the focused image.

FIELD OF THE INVENTION

A related application entitled "LOCALIZED ILLUMINATION USING TIRTECHNOLOGY" by the same inventor, is being filed on the same dayherewith and is incorporated by reference herein.

This invention relates to illumination devices and, more particularly,to a localized illumination device that uses total internal reflection(TIR) technology.

BACKGROUND OF THE INVENTION

Localized illumination is used in a variety of applications in whichnumbers, shapes, designs, icons, or other figures are to be illuminatedagainst a background of relatively darker shade. Examples of localizedillumination applications include lighting icons on computer screens,cameras, video cameras, stereos, household appliances, and variousindustrial uses, among many others.

A particular application of localized illumination is in automobiledashboard lighting. A typical automobile dashboard contains a variety ofdiscrete elements that may be illuminated for observation by someonewithin the vehicle. Elements that might be illuminated include, forexample, icons of gas pumps, oil cans, persons in seatbelts, or messagessuch as "check engine," "check oil," and "fasten safety belt."Individual elements of digits in a digital display of speed, revolutionsper minute, miles per gallon, or gallons in gas tank also requirelocalized lighting.

One alternative to a conventional automobile dashboard is a "heads-up"display in which an icon is reflected off the inside of a windshieldusing vacuum florescent displays. Such displays also use localizedillumination, but, require extremely high power.

Localized illumination for automobile dashboard lighting is commonlyaccomplished using ordinary lamps situated in wells formed in thedashboard base structure. Although lamps can be selected that emit lightin a forward direction (that is, from the light source toward the planeof the object to be illuminated), there is always some light emittedlaterally. The laterally-emitted light of a lamp may combine with thelaterally-emitted light of adjacent lamps, thereby creating areas ofincreased light, or light "hot spots," within the dashboard enclosure.Such hot spots are undesirable because of the uneven illumination thatmay result and, more commonly, because they reduce illuminationefficiency. The quality of the light generated by such dashboard lampsis diminished because much of the light that is generated is wasted bybeing emitted in a lateral direction. The forwardly-emitted light is notefficiently produced.

LED chips are also used as the light source in dashboard lightingapplications. However, because the energy emitted from LEDs tends to below, and because light from LED chips is usually emitted in fourdirections, the problem of inefficient light generation is even more ofa concern with LEDs than with ordinary lamps. It is particularlydifficult to get enough output from the LEDs to be clearly visiblethrough black dashboard covers that are currently popular in theautomotive industry. Individual LED chips are not bright enough toilluminate a desired area through such dashboard covers, particularlywhen "heads-up" displays are used.

Efforts to overcome the problem of laterally-emitted light include theplacement of plastic funnels over either the conventional lamps or theLEDs. This solution, however, is not satisfactory. The light in suchsystems is typically not all contained within the funnel, leavinginefficiencies in producing light at the plane of the illuminatedobject. In addition, such funnels are typically colored white whichscatters light in all directions and thus produces additionalinefficiencies.

No known device satisfactorily provides the efficient generation ofsufficiently bright light for use in localized illumination inapplications, such as, automobile dashboard lighting.

SUMMARY OF THE INVENTION

Briefly, the present invention provides illumination apparatus having alight source at least partially disposed in a first plane; a totalinternal reflection optical element disposed over the light source; anda light pipe disposed over the light source and the total internalreflection optical element and extending to a second plane differentfrom the first plane, wherein light emitted from the light source iscollected by the total internal reflection optical element and directedin a single direction through the light pipe, which channels the lightto the second plane so that the light emitted by the light source ismaximized at the second plane.

Advantageously, the illumination apparatus maximizes the brightness ofan object, such as an icon, digit, or other figure, requiring localizedillumination by collecting, redirecting, and channeling all or most ofthe light from a light source to a single plane at or proximate theicon, digit, or figure.

BRIEF DESCRIPTION OF THE DRAWINGS

For a better understanding of the invention, reference is made to thefollowing description of an exemplary embodiment thereof, and to theaccompanying drawings, wherein:

FIG. 1a is a perspective view of an exemplary circuit board used in anillumination apparatus constructed in accordance with the presentinvention;

FIG. 1b is a plan view of an exemplary LED arrangement mounted on thecircuit board of FIG. 1a;

FIG. 2 is a perspective view of an exemplary display housing mountedover the LED arrangement of FIG. 1b;

FIG. 3a is a side view of an exemplary total internal reflection lensused in an illumination apparatus of the present invention;

FIG. 3b is a perspective view of an exemplary light pipe used in anillumination apparatus of the present invention;

FIG. 4a is a cross-sectional front view of the light pipe shown in FIG.3b with a total internal reflection lens mounted therein;

FIG. 4b is a cross-sectional side view of the light pipe shown in FIG.3b with a total internal reflection lens mounted therein;

FIG. 5 is a cross-sectional front view of the light pipe shown in FIG.3b, with a total internal reflection lens mounted therein, mounted overan LED;

FIG. 6 is a cross-sectional side view of the light pipe shown in FIG. 5;

FIG. 7 is a cross-sectional side view of an exemplary alternative lightpipe;

FIG. 8 is a perspective view of another exemplary alternative lightpipe;

FIG. 9 is a plan view of an exemplary cover for a light pipe;

FIG. 10 is a cross-sectional front view of an exemplary alternativeillumination apparatus of the present invention;

FIG. 11 is a partially cut-away perspective view of another exemplaryalternative illumination apparatus of the present invention;

FIG. 12 is a side view of an exemplary illumination apparatus of thepresent invention in an automobile dashboard;

FIG. 13 is a perspective view of another exemplary alternativeillumination apparatus of the present invention;

FIG. 14 is a front view of another exemplary alternative illuminationapparatus of the present invention;

FIG. 15 is a side view of the illumination apparatus of FIG. 14;

FIG. 16 is perspective view of the illumination apparatus of FIG. 14;and

FIG. 17 is a front view of an automobile dashboard using localizedillumination provided according to the present invention.

DETAILED DESCRIPTION

FIG. 1 shows an exemplary circuit board 10, with electrical connectinglines 11 formed thereon, used in an illumination apparatus constructedin accordance with the present invention. Electrical connecting lines 11are formed in any desired pattern and in a conventional manner oncircuit board 10. In the illustrated exemplary embodiment, electricalconnecting lines 11 are arranged to supply power for a digital display.The light source for the display are LEDs although conventional lampsmay also be used. Surface 12 of circuit board 10 is layered with themaximum amount of metal, or other reflective material, possible in orderto provide maximum reflection of LED light off circuit board 10. This isdone so that the light reflected off surface 12 can be gathered andredirected in the forward direction. Surface 12 acts like a mirror inthis respect.

FIG. 1b shows an exemplary LED arrangement 15. LED arrangement 15 isadapted to be mounted on circuit board 10 in the desired pattern. Aplurality of LEDs 16 are mounted on a common D/A (i.e., die attached)pad 17 and connected by wires 18 to common wire bond pad 19. The LEDs 16may also be mounted on individual pads 17 on the board 10 and alsoconnected by wires 18 to individual wire bond pads 19.

FIG. 2 shows an exemplary digital display housing 20 adapted to bemounted over LED arrangement 15 on circuit board 10. Digital displayhousing 20 has placement apertures 21 formed therethrough. Digitaldisplay housing 20, LED arrangement 15, and circuit board 10 areassembled such that placement apertures 21 are located directly aboveLEDs 16 on circuit board 10. One or more LEDs 16 may be accessiblethrough a single placement aperture 21.

The problems of hot spots and insufficient illumination from LEDs 16through placement apertures 21 are overcome by the placement of anoptical element, such as a TIR lens, which, in the exemplary embodiment,is mounted in a light pipe, over at least one LED 16. FIG. 3a is a sideview of an exemplary TIR lens 25. Light beams 26 emitted laterally fromLED 16, over which lens 25 is placed, are redirected vertically by lens25 according to known principles of TIR lenses. U.S. Pat. No. 5,404,869,issued to Parkyn, Jr. et al. provides a discussion of the principlesinvolved with TIR lenses, and describes a device suitable for use in thepresent invention. The '869 patent is incorporated herein by referencefor its teachings on TIR lenses and its description of exemplarydevices.

To mount TIR lens 25 over LED 16, TIR lens 25 is first placed inside alight pipe, and the light pipe is then mounted over LED 16. FIG. 3b showan exemplary light pipe 30 that has a tapered bottom section 31 thatterminates in bottom end 32 and a top 33. Light pipe 30 is designed tofit into placement aperture 21 and over at least one LED 16.

Lens 25 is mounted within light pipe 30 as shown in FIGS. 4a and 4b. Inthe illustrated embodiment, light pipe 30 is hollow and open at bothbottom end 32 and top 33. Light pipe 30 is formed of a transparentmaterial such as polycarbonate or acrylic. Temperature tolerantmaterials should be used for light pipe 30 in applications wheretemperature extremes are expected.

The dimensions of light pipe 30, and TIR lens 25 within it, aredetermined by the location of LEDs 16 on circuit board 10 under digitaldisplay housing 20 and by certain mechanical restraints. The mechanicalconstraints include, for example, the height from the surface of circuitboard 10 to the top of placement aperture 21, the desired shape of theilluminated area, and the allowable width of placement aperture 21. Thisand other data, such as indices of refraction, are used to obtain (forexample, via computer-aided calculation and analysis) the desiredoverall TIR design according to methods known in the art as described inU.S. Pat. No. 5,404,869 which has been incorporated herein by reference.

FIG. 5 is a cross-sectional front view of light pipe 30 having TIR lens25 mounted therein and being placed in position over LED 16. FIG. 6 is across-sectional side view of light pipe 30 and TIR lens 25 over LED 16.

As shown in FIG. 5, light beams 26 emitted laterally from LED 16 areredirected vertically by TIR lens 25. Light beams such as beam 27emitted vertically from LED 16 pass through TIR lens 25 withoutdirectional change. Beams such as beam 28 that are emitted down from LED16 are reflected off surface 12 of circuit board 10, which is metallizedto act as a mirror. Reflected beam 28 then strikes TIR lens 25, ineffect, as a laterally emitted beam from LED 16. Beam 28 is thenredirected vertically with the other beams 26, 27. In this manner, lightfrom LED 16 is maximized at the plane defined by top 33 of light pipe30. Using the present invention in the illustrated embodiment, theindividual bars or elements of the digits in display housing 20,represented by placement apertures 21, are illuminated brightly enoughfor automobile dashboard applications. Each LED 16 in each placementaperture 21 may be turned on and off individually as desired.

Use of the present invention for a digital display is only one of avariety of applications of the present invention. In other applications,alternative embodiments of the individual elements, such as light pipe30, may be used. For example, as shown in FIGS. 7 and 8, light pipe 30may be configured so as to have a constricting or tapered shape. In FIG.7, light pipe 30 is conical with bottom end 32 having the largestdiameter. TIR lens 25 is disposed at the bottom of light pipe 30 whereit gathers the output from LED 16 and redirects it up through light pipe30. Because of the taper in light pipe 30, all of the light is thenchanneled to a smaller diameter plane at top 33. Since the amount oflight is substantially conserved in light pipe 30 and funnelled to asmaller diameter, the brightness of the light at the plane at top 33 ishigher than if light pipe 30 were not tapered and top 33 had the samediameter as bottom end 32. More light is emitted per unit area in such adesign.

Similarly, FIG. 8 shows a tapered structure for light pipe 30 in apie-shaped design. LED 16 and TIR lens 25 are contained in bottomsection 31 of light pipe 30. Light pipe 30 has the largest horizontalcross-sectional plane at bottom end 32 and tapers to its narrowest crosssection at top 33. As in FIG. 7, the LED light is collected andredirected by TIR lens 25 and then channeled to a smaller diameter planeat top 33, where the light is effectively brighter.

Another exemplary application for the present invention is theillumination of icons. This may be accomplished in several ways. FIG. 9illustrates an exemplary cover 40 adapted to be disposed over top 33 oflight pipe 30. Cover 40 may be shaped to match the shape of top 33 andmay be integrally molded to top 33. Cover 40 may also be a film placedover top 33. Further, cover 40 may be integrally formed as part of lightpipe 30 so that light pipe 30 is hollow but closed at top 33.

Cover 40 has an icon 41 configured therein. Icon 41 will be illuminatedto convey information to a viewer. In the illustrated embodiment, icon41 is a gas pump for use in an automobile dashboard display. Thus, inthis case, the driver of an automobile may be alerted of a low tank ofgas when icon 41 illuminates.

Cover 40 may be constructed of the same material as light pipe 30, withicon 41 cut or stamped out of cover 40. Alternatively, cover 40 may bemolded with icon 41 therein. Cover 40 may also be tapered to a raisedplane in which icon 41 is configured. When illuminated, light emittedfrom LED 16 is collected by TIR lens 25 and directed through light pipe30, which channels the light to the plane at cover 40 over top 33. Allof the LED light is emitted through icon 41, creating a bright, visiblefeature.

In all of the embodiments discussed herein, and as described above, aplurality of LEDs 16 may be placed within a single light pipe 30. Asshown in FIG. 10, six LEDs 16 are disposed under TIR lens 25 withinlight pipe 30. LEDs 16 may be all of the same color, creating addedbrightness by the plural number of light sources. Alternatively, some orall of LEDs 16 may be of different colors, to be illuminated separatelyor in combination to create different colors for illumination.

For example, as shown in FIG. 11, icon 41 of a gas tank in cover 40 atoplight pipe 30 may be illuminated with green light from the LEDs when thegas tank is full. Circuit board 10 may be programmed or controlled toilluminate only green LEDs 16a and 16b. As the tank empties, yellow LEDs16c and 16d may be illuminated such that the driver sees a change in thecolor of icon 41 from green to yellow. When the tank is very low infuel, red LEDs 16e and 16f may be illuminated such that the icon changesto red. Alternatively, only red and green LEDs 16a , 16b, 16e, and 16fmay be used, all of which can be activated to shine in combination tocreate a yellow color for icon 41 at the desired time. This combined useof colored light from the LEDs may avoid excess material and energy use,eliminating the need for separate colored LEDs such as yellow LEDs 16cand 16d.

As noted above, the multicolor LEDs 16 may also be used with the digitaldisplay housing 20 discussed above. So, for example, in an automobiledashboard application, the multicolor LEDs 16 can be used to illuminatea digital display of the car speed, e.g., green below 55 miles per hour(mph), yellow between 55 and 65 mph, and red above 65 mph.

Another use of the present invention in an automobile dashboardapplication may be to have several light pipes 30, with LEDs 16underneath them, arranged in an arc behind the numbers on an analogspeedometer for illumination. FIG. 12 shows an exemplary illuminationapparatus with light pipe 30 mounted in an automobile dashboard 61. Icon41 becomes visible when LEDs 16 (not shown) beneath light pipe 30 areilluminated.

FIG. 13 illustrates another way of illuminating icon 41 using thepresent invention. The figure shows that an entirely separate piece 45with icon 41 configured therein may be used, instead of cover 40, incombination with light pipe 30. In this case, light pipe 30 acts as abacklight, maximizing the light at the plane at top 33 for illuminationof icon 41. Separate piece 45 is spaced apart from light pipe 30 and maybe a part integral to the display structure itself, such as anautomobile dashboard, with light pipe 30 illuminating it from behind.

FIGS. 14 and 15 show an alternative illumination apparatus wherein alens 50 is disposed over top 33 of light pipe 30. Lens 50 may furthernarrow the plane in which light from LEDs 16 are concentrated, thusenhancing the brightness of light at that plane. Lens 50 may be a simplecylindrical lens or a flat holographic lens. In the latter case, theholographic lens is used to narrow the field of view instead of as adiffuser to spread out the field of view.

Using lens 50 in combination with light pipe 30 is particularlyapplicable to situations in which the field of view is well-defined. Forexample, in an automobile, because the driver's eyes must be below theroof of the car and above the steering wheel, there is a predefined areain which the image may be focused. By narrowing the plane of focus tothis defined area, it is possible to further brighten an illuminatedicon 41.

FIG. 16 illustrates use of lens 50 on light pipe 30 to focus light atthe plane at which a separated icon 41 is located. Alternatively, ofcourse, icon 41 may be formed on a cover 40 of light pipe 30 beneathlens 50, such that the image of icon 41 is focused to the desired plane.

The overall effect of the use of the present invention is illustrated inFIG. 17 which shows an automobile dashboard using localizedillumination. Icons 41 are visible through a black dashboard cover/panel61 because of the added brightness contributed by illumination apparatusof the present invention.

The illumination apparatus of the present invention is not used to imageLED 16. Similarly, the light from LED 16 is not projected. Rather, thelight from LED 16 is collected and directed to a single plane tomaximize the output of LED 16 in automotive dashboard lighting and otherapplications.

The embodiments described herein are merely illustrative of theprinciples of the present invention. Various modifications may be madethereto by persons ordinarily skilled in the art, without departing fromthe scope or spirit of the invention.

For example, although the embodiments discussed herein pertain to use inan automobile dashboard, embodiments of the invention useful in otherapplications, such as traffic lights, computers, cameras, video cameras,stereos, and household appliances, are considered to be within the scopeof the invention.

Further, as noted above, alternative embodiments of the individualelements may be used. For example, light pipe 30 may be hollow with aclosed top 33 and used in combination with lens 50, cover 40 and/orseparate piece 45.

Further, the light emitted by the light source can include radiationhaving wavelengths outside the visible light spectrum, such as, infraredand ultraviolet. In such case, the increased visibility of an object tobe viewed can be accomplished via a different physical reaction, e.g.incandescence, fluorescence, etc.

What is claimed is:
 1. Illumination apparatus, comprising:(a) a lightsource at least partially disposed in a first plane; (b) a totalinternal reflection optical element disposed over the light source; and(c) a light pipe disposed over the light source and the total internalreflection optical element and extending to a second plane differentfrom the first plane,wherein light emitted from the light source iscollected by the total internal reflection optical element and directedin a single direction through the light pipe, which channels the lightto the second plane so that the light emitted by the light source ismaximized at the second plane.
 2. The illumination apparatus of claim 1,wherein the light source is a light emitting diode.
 3. The illuminationapparatus of claim 1, wherein the light source comprises a plurality oflight emitting diodes.
 4. The illumination apparatus of claim 3, whereinat least some of the light emitting diodes are of different colors fromone another.
 5. The illumination apparatus of claim 1, wherein the lightpipe has a tapered configuration.
 6. The illumination apparatus of claim1, wherein the light pipe is configured to have the largestcross-sectional area at the end of the light pipe disposed in the firstplane and the narrowest cross-sectional area at the end of the lightpipe disposed in the second plane.
 7. The illumination apparatus ofclaim 1, further comprising a cover that is at least partiallytranslucent disposed in the second plane over the light pipe.
 8. Theillumination apparatus of claim 7, wherein the cover has an iconconfigured therein, such that said icon is illuminated by the lightemitted from the light source.
 9. The illumination apparatus of claim 7,wherein the cover is integrally molded to the light pipe.
 10. Theillumination apparatus of claim 1, further comprising a cover that is atleast partially translucent and has an icon configured therein, saidcover being disposed in a third plane over the light pipe and apart fromthe light pipe, such that the icon is illuminated by the light emittedfrom the light source to the second plane.
 11. The illuminationapparatus of claim 1, wherein the light pipe has a closed end at thesecond plane, said closed end being at least partially translucent. 12.The illumination apparatus of claim 11, wherein the closed end of thelight pipe has an icon configured therein, such that said icon isilluminated by the light emitted from the light source.
 13. Theillumination apparatus of claim 12, further comprising a lens disposedin the second plane over the closed end of the light pipe so that theicon is illuminated by the light emitted by the light source and theimage of the icon is focused by the lens to a third plane apart from thelight pipe.
 14. The illumination apparatus of claim 11, furthercomprising a cover that is at least partially translucent and has anicon configured therein, said cover being disposed in a third plane overthe light pipe and apart from the light pipe, such that the icon isilluminated by the light emitted from the light source to the secondplane.
 15. The illumination apparatus of claim 11, further comprising:a) a lens disposed in the second plane over the closed end of the lightpipe to focus light emitted from the light source at a third plane apartfrom the light pipe and b) a cover that is at least partiallytranslucent and has an icon configured therein, said cover beingdisposed in the third plane such that the icon is illuminated by thelight emitted from the light source and focused by the lens.
 16. Theillumination apparatus of claim 1, further comprising a lens disposed inthe second plane over the light pipe.
 17. The illumination apparatus ofclaim 16, wherein the lens is a simple cylindrical lens.
 18. Theillumination apparatus of claim 16, wherein the lens is a holographiclens.
 19. The illumination apparatus of claim 16, further comprising: a)a lens disposed in the second plane over the light pipe to focus lightemitted from the light source at a third plane apart from the light pipeand b) a cover that is at least partially translucent and has an iconconfigured therein, said cover being disposed in the third plane suchthat the icon is illuminated by the light emitted from the light sourceand focused by the lens.
 20. The illumination apparatus of claim 1,further comprising: a) a lens disposed in the second plane over thelight pipe and b) a cover that is at least partially translucent and hasan icon configured therein, said cover being disposed between the lensand the light pipe so that the icon is illuminated by the light emittedby the light source and the image of the icon is focused by the lens toa third plane apart from the light pipe.
 21. The illumination apparatusof claim 1, wherein the light source is mounted on a substrate that isat least partially reflective, such that said substrate reflects lightfrom the light source to the total internal reflection optical element.22. Apparatus for use in an illuminated display, comprising:(a) a lightemitting diode mounted on a metallized substrate; and (b) a totalinternal reflection lens mounted over the light emitting diode thatcollects light emitted from the light emitting diode and light reflectedfrom the metallized substrate and directs the light in a singledirection.
 23. The apparatus of claim 22, further comprising:(a) a lightpipe disposed over the light emitting diode and the total internalreflection lens, said light pipe having walls extending from thesubstrate to a plane above the substrate, such that directed light fromthe total internal reflection lens is channeled through the light pipeto said plane; and (b) a lens disposed in said plane over the light pipethat focuses the channeled light to a respective second plane.
 24. Theapparatus of claim 22, further comprising:(a) a light pipe disposed overthe light emitting diode and the total internal reflection lens, saidlight pipe having walls extending from the substrate to a plane abovethe substrate, such that directed light from the total internalreflection lens is channeled through the light pipe to said plane; and(b) a cover disposed in said plane over the light pipe, said coverhaving an icon configured therein, such that the icon is illuminated bythe light from the light emitting diode; and (c) a lens disposed overthe cover of the light pipe that creates a focused image of the icon sothat the light emitted by the light emitting diode is maximized at saidfocused image.
 25. The apparatus of claim 22, further comprising:(a) alight pipe disposed over the light emitting diode and the total internalreflection lens, said light pipe having walls extending from thesubstrate to a plane above the substrate and having a closed end, withan icon configured therein, at said plane, such that directed light fromthe total internal reflection lens is channeled through the light pipeto said plane and the icon is illuminated by the light from the lightemitting diode; and (b) a lens disposed over the closed end of the lightpipe that creates a focused image of the icon so that the light emittedby the light emitting diode is maximized at said focused image.
 26. Anilluminated display, comprising:(a) a display panel having at least onesymbol formed therein for viewing by an observer, and (b) anillumination device that has a light source, an optical element thatcollects light from the light source and directs the light in onedirection using total internal reflection, and a light pipe thatchannels the light from the optical element to illuminate the symbol inthe display panel.
 27. The display of claim 26, wherein the opticalelement comprises a base upon which the light source is mounted thatreflects light emitted from the light source.
 28. The display of claim26, wherein the light pipe is configured to channel light from theoptical element to illuminate the symbol with increased brightness. 29.The display of claim 26, wherein the light pipe is configured to channellight from the optical element to illuminate the symbol with increasedintensity.
 30. The display of claim 26, wherein the light pipe ismounted in the display panel and has the symbol formed therein.
 31. Thedisplay of claim 26, wherein the light pipe has a lens to focus thechanneled light to illuminate the symbol.
 32. The display of claim 26,wherein the light pipe is mounted in the display panel and has thesymbol formed therein and has a lens formed over the symbol to focus theimage of the symbol to a respective plane apart from the display panel.